Perfluoroalkylimidazolines



United States *PERFLUOROALKYLIIVIIDAZOLINES r This invention relates to a novel class of compounds 7f iuscful as corrosion inhibitors and is a division of applicationSN. 587,493, filed'May- 28, 1956, which concerns hovel-corrosion inhibitor compositions.

-- -.High-mo1ecular weight alkylimidazolines have been utilized for several known purposes,-such as the improve- -ment'of adhesion between mineral aggregates and asphalt and for-inhibiting thecorrosion of casings-and tubing in gas condensate wells and the like. However, the action of 'these material'shas not'beenfully'satisfactory "due either to their thermal instability, their lack of high surface activity, or their merely partial effectiveness as corrosion inhibitors.

' -Hydrocarbon systems generally-must beimproved in oneirespect or another-with regard to their surface active properties. For example, gasolines, especially in 1 the presence oftraces ofwater or water vapor, permit cr I I: r'osion of motor parts, and are subject to icing-difficulties at relatively'low temperatures. Asphalts, although they cbntain small amounts ofnaturallyoccurring polar bodies', do not firmly adhere to many mineral aggregates, es- -pecially wh'en the latter are damp at the time the asphalt is. applied thereto. a Lubricating oils are well' known to behighly corrosive to metals with which they come in contact, especiallywhen they contain oxidation or decomposition residues. Greases are subject'to the same difiiculties and the newer type of greases, namely, those gelled with a non-soap gelling agent, are'subject to another' shortcoming, namely, the deleterious attack of water upon the gelling agent. Oil and "gas condensate wells are'alsosubjectcd to intensive "ge'neral or localized cdrrOsiondueeitht to the pr'e'sence of sa-lt' u'later or to the presence of sulfide-forming bacteriaJ Many diverse types of additives 'have been employed for overcoming each of the recited difiiculties,-butlimitations are present in each 'class ofcompositions detailed-{above :Wlth respect to' the maximum-amount Which-may be utilized due to side eifects-which- -may;-appear.-----For ---example, if too large anamountof an additiVe-isemployedin a lubricating oil for preventing corrosiontherein, the oil issubject to theformationof-excessivesludge deposits and gum.

It isan object of the present inventiontozprovide a I atent surprisinglyhigh surface activity, thermal stability-{and corrosion preventive characteristics ineitheraque'ous or a hydrocarbon systems.

1,2-diaminoalkane compound and the acid chloride of at least one perfluoro fatty-acid. These amides are then subjected to a cyclizing heating'operation inorder to eliminate water and form: Z-perfluoroalkylimidazolines which have the following general structuret %l- ICHY n 2n+1 l r HY wherein n is an integer from lto. 19 Xvis H, a lower aminoalkyl radical (RNH of 2 to 3=carbon atoms or a lower hydroxyalkyl radical ROH) of 2 to 3 carbon atoms, and one of the Ys is H and the other one is H or an alkyl radical of I to 19 carbon atoms.

Ethylene diamine may be employed per se or it'may be as any low molecular weight homolog or polymer thereof such aspropylene diamine, diethylenetriamine, triethylenetetraarnine "and tetraethylene pentaamine. However, the preferred species is ethylene diamine per se. Attempts to condense the ethylene diamines'with perfluoro "fatty acids directly resulted in the formation of perfluoro alkanesyindicating that decarboxylation occurred during the attempted condensation. Therefore, it was foundnecessary to convert the perfluoro fatty acids to the corresponding acid' chloride before reacting with ethylene diamine. The acid chlorides are preferably formed by reaction of the perfluoro fatty acid with a molar excess of thionyl chloride for a period of 1-96 hours at temperatures between about 10 and C. Ex-

cess thionyl chloride and volatile reaction products are 7 then removed, such as by vacuum stripping, the product constituting principally the'acid chloride of the original perfluoro fatty acid. This acid chloride is then added 7 to a molar excess of ethylene diamine to form the salt (or amide); which is then heated at atmospheric pressure or at reduced pressure to remove water and excess 9 ethylene diamine. When all of the Water of condensation has been-removed, such as by distillation, the reaction product so obtained is neutralized, such as by addition of an excess amount of a basic materiaL-typically,

I sodium hydroxide The product is thenextracted with a water-immiscible solvent such as ether or the like'and dried, preferably over calcium r sulfate, to obtainthe desired -2-perfiuoroalkylimidazoline.

1 The heating period following elimination of excess thionyl chloride is for the purpose of causing cyclization of the initial reaction product by elimination of water. This may be conducted at temperatures between about 'and 200* 0., preferably in the range from about to about C. The cyclizing period at these temperatures will normally be between about 1 and about 3 hours.

The products so formed, due to their relatively high fiuorine-to-carbon-ratio, have only a limited solubility in either water or hydrocarbon systems. 'When solubility in water is desired, it is preferred that'the mono- I about 5 to about 20 carbon atoms per molecule.

The perfluoro fatty acids to be utilized in the formation of the subject class of'imida'zolines include those having from l'to 20 carbon atoms per molecule including the per fluoro derivatives of acetic, propionic, butyric, valeric, caproic, caprylic, capric, lauric, myristic, palmitic, stearrc and arachidic acids. The fatty acids to be utilized in the I formation of the mono-fatty acid salts of the perfluoroalkylimidazolines constitute one ormore of the nonfluorinated fatty acid series.

The salts of the perfiuoroalkylimidazolines are formed simply by addition of an equi-molecular amount of the fatty acid to a solution of the imidazoline. Of course, unsaturated aliphatic monocarboxylic acids may be used in place of the saturated varieties listed above. The principal unsaturated acid especially useful in the preparation i of a product of diverse utility and solubility is oleic acid.

Species of' the above-described reaction products include the following:

Substituted perfluoroalkylimidazolines:

2-perfluorooctyl-3-aminoethylimidazoline 2-perfluorohexyl-4-octadecylimidazoline 2-perfluorododecyl-5 -octylimidazoline 2-perf1uorooctyl-3 -hydroxyethylimidazoline Salts of perfluoroalkylimidazolines:

2-perfluoroheptylimidazolinium acetate Z-perfluorooctylimidazolinium oleate 2-perfluorononylimidazolinium caproate 2-perfiuorododecylimidazolinium butyrate 2-perfiuoroheptylimidazolinium stearate The above-described perfluoroalkylimidazolines and their salts are usefulin both aqueous media and in hydrocarbon media where corrosion inhibition is desired or required. For example, the water-dispersible species described above are especially useful in aqueous acid media for depressing corrosion normally caused by said acids of metallic containers or other metals coming in contact therewith. For example, the addition of from about 0.1 to about 1% by weight of a water-dispersible perfluoroimidazoline salt in aqueous hydrochloric or sulfuric acids results in a remarkable reduction in the rate of corrosion caused by these acids. More particularly, when the acids contain from 50 to 99% Water, they may be disastrously destructive to metals in contact therewith in a short space of time. However, the addition, for example, of 0.1% by weight of Z-perfluorooctylimidazoline to a aqueous HCl solution reduced the corrosion of carbonsteel at room temperature after 21 4 H has been found to substantially reduce the tendency of the fuel to cause icing difiiculties.

The addition of between about 0.1% and about 1% by weight of the oleophilic perfluoroalkylimidazoline salts to hydrocarbon lubricating oils and greases causes a substantial reduction in the rate of corrosion caused by the lubricating oil with respect to a wide variety of metals in contact therewith, including aluminum, steel, copper, nickel and silver. This is true not only at room temperature and below, but also at temperatures in the order of about 175 C. The lubricating oil containing the indicated quantity of imidazoline salt may, of course, be the major ingredient of a grease composition. Another allied use of the subject additives is in the formation of grease compositions wherein an inorganic grease-forming colloid such as silica, clay or other hydrophilic material is coated with approximately a monomolecular layer of the waterresistant perfluoroalkylimidazoline or its salt and thereafter dispersed in a lubricating oil to form a grease composition therewith. Normally when used for this additional function, the proportion of imidazoline compound is between about 10% and about 100%, based on the weight of the inorganic gelling agent. It is preferably added to the inorganic colloid while the latter is in an expanded condition in an aqueous medium, whereupon the imidazoline is preferentially adsorbed by the surfaces of the colloid material.

The corrosion of crude oil or gas condensate well metallic parts such as casings, tubings and the like is a problem of enormous economic concern, since the withdrawing and replacement of these parts of an operating well entail the expenditure of hugh amounts of money, not only in the replacement materials involved, but also in the loss of production during a replacement period. The presence of acidic gases such as 80;, H 8 and CO in the water produced together with the gas or petroleum hours from an infinitely high corrosion rate wherein the specimen was destroyed to a corrosion rate of only about 15 mils per year. The inhibition of corrosion caused by concentrated aqueous sulfuric acid can be effected with the same imidazoline by the addition of about 0.1% by weight to reduce the disastrously high corrosion rate of carbon steel caused thereby to a rate in the order of 40 mils per year.

It has been found that the present Z-perfiuoroalkylimidazoline salts are highly effective for the reduction in corrosion caused by gasoline in the presence of salty water when they are utilized in amounts varying from about 01101 to about 0.1% by weight of the gasoline or other fuel such as gas turbine fuels and the like. The latter may comprise kerosene or gas oil and, especially when utilized in aircraft, the volatile fuel in the presence of water or water vapor is subject to ice formation which in turn causes plugging of fuel line filters. The presence of the indicated quantity of perfluoroalkylimidazoline salt well if preferred or practical.

crude oil normally aggravates the corrosion problems involved. However, ithas been found that the .addition of between about 0.005 and 0.1% by weight, based on 'the aqueous phase, of the perfiuoroalkylimidazoline or its salt causes a marked reduction in the rate of corrosion caused by the system in theabsence of oxygen comprising a hydrocarbon fluid, salty water and H 8 orCO The perfluoroalkylimidazoline compound may be injected continuously or intermittently into the well, preferably in the annular space between the casing and tubing, but may be injected through the tubing at the bottom of the The following examples illustrate the preparation of the subject 2-perfiuoroalkylimidazolines and their use in the protection of representativeaqueous and hydrocarbon systems:

Examplel 200 parts by weight of perfluorocaprylic acid was stirred with a molar excess of thionyl chloride at room temperature for about 48 hours. Excess thionyl chloride Was'stripped from the product, which comprised the acid chloride of perfluorocaprylic acid. This product was added to a molar excess (50 parts by weight) of ethylene diamine at room temperature to form the corresponding amide. The amide was heated atatmospheric pressure for conversion to the imidazoline by elimination of water and cyclizing of the product.

Heating also removed excess ethylene diamine. Water was continuously distilled until a temperature of 132 C. was reached (2 hours). The cyclized product was neutralizedwith300 parts by weight of 10% aqueous sodium hydroxide, ether extracted and dried over calcium chloride to obtain the product, which was 2-perfiuoroheptylimidazoline which contained 64% by weight of fluorine and 5.7% by weight of nitrogen.

The product had only a moderate solubility in gasoline and, in order to convert this to a gasoline-soluble material, it was reacted with oleic acid in an equimolar amount to form the monooleate of the imidazoline.

Example 11 A straight run gasoline (80 cc.) was contaminated with 1 cc. of 0.05% aqueous sodium chloride. The contaminated gasoline was left at room temperature in the presence of air in contact with a carbon steel strip, being rotated at 60 r.p.m. for about 18 hours. At the end of this period, it was found that the test strip was badly corroded. In a parallel test, but in which 0.003% by weight of the imidazoline oleate compound produced as described in Example I was also added to the gasoline, only a minor amount of corrosion of the strip occurred.

Example III A more severe gasoline corrosion test is conducted by submerging a carbon steel plate 2 /2 inches square in the gasoline, after which a single drop of salt water is placed on the plate. In the absence of any inhibitor, severe rusting of the plate occurred in 15 minutes. The presence of 0.01% by weight of the imidazoline oleate formed according to Example I prevented any corrosion up to a period of about 6 hours. The presence of 0.001% by weight of the imidazoline oleate prevented corrosion for 3 hours.

Example IV Carbon steel was immersed in a aqueous hydrochloric acid solution. The steel strip commenced to disintegrate rapidly at room temperature. The addition of 0.1% by weight, based on the hydrochloric acid solution, of the imidazoline prepared according to Example I reduced the corrosion rate at room temperature to approximately mils per year.

Example V Concentrated aqueous sulfuric acid disintegrates carbon steel at a high rate of corrosion at room temperature. However, the addition of 0.1% by weight of the imidazoline prepared according to Example I reduced the corrosion rate to about 42 mils per year.

Example VI In order to simulate the conditions present in gas condensate wells, tests were carried out in 4-ounce oil sample bottles, containing a x 5%" sandblasted specimen of cold rolled carbon steel. The bottles contained 50 cc. kerosene, 10 cc. distilled water which contained 3% sodium chloride, 0.1% calcium chloride, 0.03% magnesium chloride, and 0.1% acetic acid. The bottles were rotated end-over-end at r.p.m. for 24 hours at F. The specimens were then cleaned by immersing with gentle action for 1 minute in concentrated hydrochloric acid containing 5% SnCl and 2% Sb O The specimen was then neutralized immediately in sodium bicarbonate solution, rinsed with water and dried. Controlled cleaning loss was 3 milligrams and the corrosion rate was calculated from net weight loss. In the absence of any inhibitor in the system, the specimen of steel corroded at a rate of about 53 mils per year. The presence of 0.01% of the imidazoline oleate prepared according to Example I about reduced the corrosion rate under the same conditious to less than 10 mils per year.

I claim as my invention:

1. A compound of the group consisting of compounds of the formula:

N-CH,

wherein n is an integer from 1 to 19.

3. The fatty acid salt of the compound defined in claim 2 wherein the fatty acid contains from 1 to 20 carbon atoms.

4. The salt according to claim 3 wherein the fatty acid contains from 5 to 20 carbon atoms.

5. 2-perfluoroheptylimidazoline.

6. The oleic acid salt of 2-perfluoroheptylimidazoline.

No references cited. 

1. A COMPOUND OF THE GROUP CONSISTING OF COMPOUNDS OF THE FORMULA: 